1. Field of the Invention
The invention pertains to the field of manual transmissions. More particularly, the invention pertains to manual transmissions using a chain and planetary gear set as the final drive.
2. Description of Related Art
In the present automobile market, there is a constant search to decrease the package size of components and increase the efficiency of the engine components.
Efficiency and package size improvements have been made in automatic transmissions. For example, in the GMPT 6T40 and 6T45, which are currently in production and shown in prior art FIG. 1, the layshaft of the automatic transmission has been removed and a chain 8 surrounds the input sprocket 4 coupled to the transmission output shaft (not shown) and an output sprocket 6 coupled to the sun gear 16 of a planetary set. The sun gear 16 is driven by the output sprocket 6, driving the planet carrier 18 and the differential 20, formed as one piece. The ring gear 12 is fixed to the housing 10.
FIG. 2 shows a conventional manual transmission. In a conventional manual transmission, the pinion gear 5 is coupled to the manual transmission output shaft 2. The pinion gear 5 is meshed with and drives a ring gear 7. The ring gear 7 is coupled to the differential housing and the differential 20, directly driving the differential 20, which in turn drives the front axles 15 to the wheels. The ring gear 7 has a large mass, large rotational inertia, and is very large in diameter, measuring to be approximately 200-220 mm in diameter. The ring gear 7 rotates in an opposite direction from the manual transmission output shaft 2 with a 3 to 4 times speed reduction. By using such a large diameter ring gear 7, a 3.5 to 1 speed reduction ratio is achieved at the cost of engine compartment space and large manual transmission packaging.
While efficiency and package size have been improved in automatic transmissions, no effort has been made to do so in transmissions with geared final drives which have a reverse direction geared output, such as dual clutch transmissions, automated manual transmissions, hybrids, electric, CVT, two axis manual transmissions, and three axis manual transmissions.